Optical semiconductor module

ABSTRACT

An optical semiconductor module including a base having installed on an optical fiber and an optical semiconductor element, and a package which houses the base on a bottom thereof and has a first side wall with an optical section through which the optical fiber is led and a second side wall facing the first side wall, where the base is cut off to form a curved surface with respect to the bottom at a lower corner on a side of the base facing the second side wall of the housing, and a ratio of r/t is from 0.4 to 1.0, where t is a thickness of the base, and r is a curvature radius of the curved surface.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of and claims the benefit under 35U.S.C. § 120 from parent application, U.S. Ser. No. 11/837,084, (U.S.Patent Publication No. 2008/0031567 A1) filed Aug. 10, 2007, which is acontinuation of U.S. Ser. No. 10/460,405 (U.S. Patent Publication No.2003/0235377 A1) filed, Jun. 13, 2003 and claims the benefit of priorityunder 35 U.S.C. § 119 from Japanese Patent Application No. 2002-174969,filed Jun. 14, 2002, the entire content of the parent application isincorporated herein by reference.

BACKGROUND OF THE INVENTION

1) Field of the Invention

The present invention relates to an optical semiconductor module havingan optical semiconductor element and an optical fiber that are used foroptical communications.

2) Description of the Related Art

FIG. 23A is a plan view of a part of a conventional semiconductor laserdiode (hereinafter, “LD”) module, and FIG. 23B is a longitudinalcross-sectional view of the part. The LD module includes a base 6 ontowhich a heat sink 3 and a carrier 5 are soldered. On the heat sink 3, anLD element 1 and a thermistor 2 are mounted, and on the carrier 5, aphoto diode (hereinafter, “PD”) element 4 is mounted. Further, a metalferrule 7 a supporting an optical fiber 7 is fixed onto the base 6 viatwo support members 6 a by YAG laser welding or with solder. The weldingpoints, in the drawings, are denoted by solid circles P_(wd). Theoptical fiber 7 is precisely aligned so as to be optically coupled witha laser beam emitted from the LD element 1, and is fixed onto thesupport member 6 a.

FIG. 24 is a longitudinal cross-sectional view of the conventional LDmodule, where the base 6 is accommodated within a package 8, and isfixed onto a bottom plate 8 e of the package 8. The package 8 is sealedwith a lid 9 at the upper opening, thereby to complete the assembly ofthe LD module. A lensed fiber, one end of which being formed in aspherical or a wedged shape to serve as a lens portion, is used as theoptical fiber 7 in order to ensure a high coupling efficiency betweenthe optical fiber 7 and the laser beam emitted from the LD element 1.The other end of the optical fiber 7 is led out of the package 8 througha longitudinal hole 8 a of a snout 8 b prior to mounting of the base 6onto the bottom plate 8 e of the package 8. A portion between theoptical fiber 7 and the internal wall of the snout 8 b is hermeticallysealed with sealant S like solder or synthetic resin.

The LD module, particularly one using the lensed fiber, requires thatthe LD element 1 and the lensed fiber are coupled with an extremely highprecision, and that the optical fiber 7 and the support member 6 a areprecisely positioned.

In the LD module shown in FIG. 24, the base 6 is directly fixed onto thebottom plate 8 e, with no Peltier module for cooling interposed. Thelongitudinal hole 8 a in FIG. 24 is formed through a front wall 8 c ofthe package 8 at a position far down from the upper end of the frontwall 8 c. Such position of the longitudinal hole 8 a makes the mountingof the base 6 difficult.

FIG. 25 is a longitudinal cross-sectional view of the conventional LDmodule in the mounting step. In the mounting step, the base 6 isaccommodated onto the bottom plate 8 e, maintaining a state that theoptical fiber 7 passes through the longitudinal hole 8 a. In such asituation, a position of the metal ferrule 7 a holding the optical fiber7 is limited by the position of the longitudinal hole 8 a, causing oftenan interference between a lower portion of the base 6 and a rear wall 8d of the package 8 when mounting the base 6, depending on sizes of thepackage 8 and the base 6. And while the base 6 is being mounted onto thebottom plate 8 e of the package 8 so as to avoid the interference,stress is often applied to the optical fiber 7 and thereby the opticalfiber 7 is bent, pressed, or pulled. In this way, this stress oftencauses misalignment between the LD element 1 and the optical fiber 7.

Further, in the mounting step, the optical fiber 7 is often excessivelybent at a portion A encircled by a dashed line in FIG. 25, by contactwith the snout 8 b. In some cases, the optical fiber 7 is coated withmetal (e.g., gold), in order to facilitate the hermetic sealing of theoptical fiber 7 inside the inner space of the snout 8 b with solder S orother sealant ,or in order to facilitate the soldering of the opticalfiber 7 to the base 6. Such metal-coated optical fibers have a minimumallowable bending curvature radius larger than that of non-coatedoptical fibers and are more repulsive against the bending deformation.Therefore, the optical fiber 7 needs to be handled so as not to be benttoo much. The similar situation may be present not only in opticalsemiconductor modules in general of butterfly-type, including receivermodules (hereinafter, “PD modules”) having a PD element mounted on thebase 6, but also in the LD module of so-called DIL (Dual In Line) typewhich utilizes a small-sized package.

SUMMARY OF THE INVENTION

The optical semiconductor module according to one aspect of the presentinvention includes an optical semiconductor element; an optical fiberoptically coupled with the semiconductor element; a base having an uppersurface and a lower surface, the optical fiber and the opticalsemiconductor element being mounted on the upper surface; and a packagehaving a bottom plate on which the base is directly mounted, a frontwall having a hole through which the optical fiber is inserted, and arear wall opposite to the front wall, wherein the base has a rear faceformed on an end portion opposite to the front wall, the rear face beingpositioned above the lower surface.

The optical semiconductor module according to another aspect of thepresent invention includes an optical semiconductor element; an opticalfiber optically coupled with the semiconductor element; a base having anupper surface and a lower surface, the optical fiber and the opticalsemiconductor element being mounted on the upper surface; a packagehaving a bottom plate on which the base is directly mounted, and a frontwall having a hole through which the optical fiber is inserted; and alid having a first portion disposed above the base and a second portionfacing the hole, the first portion and the second portion of the lidbeing combined with each other to cover the package.

The other features and advantages of the present invention arespecifically set forth in or will become apparent from the followingdetailed descriptions of the invention when read in conjunction with theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a longitudinal cross-sectional view of a LD module accordingto a first embodiment of the present invention;

FIG. 2 is a top plan view of a package of the LD module shown in FIG. 1;

FIG. 3 is a longitudinal cross-sectional view of a part of the LD moduleshown in FIG. 1;

FIG. 4 is a longitudinal cross-sectional view of the LD module in themounting step;

FIG. 5A and FIG. 5B are longitudinal cross-sectional views of otherexamples of a base of the LD module;

FIG. 6A is a top plan view of other example of the base, and FIG. 6B isa longitudinal cross-sectional view of the base shown in FIG. 6A;

FIG. 7 is a longitudinal cross-sectional view of a LD module accordingto one example of a second embodiment of the present invention;

FIG. 8 is a longitudinal cross-sectional view of the LD module shown inFIG. 7 in the mounting step;

FIG. 9 is a longitudinal cross-sectional view of a LD module accordingto another example of the second embodiment in the mounting step;

FIG. 10 is a longitudinal cross-sectional view of a LD module accordingto still another example of the second embodiment in the mounting step;

FIG. 11 is a longitudinal cross-sectional view of a LD module accordingto still another example of the second embodiment in the mounting step;

FIG. 12 is a longitudinal cross-sectional view of a LD module accordingto still another example of the second embodiment in the mounting step;

FIG. 13 is a longitudinal cross-sectional view of a PD module accordingto a third embodiment of the present invention;

FIG. 14A is a top plan view of one example of a base used for the PDmodule shown in FIG. 13, and FIG. 14B is a side view of the base shownin FIG. 14A;

FIG. 15 is a longitudinal cross-sectional view of the PD module shown inFIGS. 14A and 14B in the mounting step;

FIG. 16 is a side view of a LD module according to a fourth embodimentof the present invention;

FIG. 17 is a top plan view of the LD module shown in FIG. 16;

FIG. 18 is a longitudinal cross-sectional view of a LD module accordingto a fifth embodiment of the present invention;

FIG. 19 is a longitudinal cross-sectional view of the LD module shown inFIG. 18 in the mounting step;

FIG. 20 is a longitudinal cross-sectional view of another example of theLD module according to the fifth embodiment, having a different packagefrom that shown in FIG. 18;

FIG. 21 is a longitudinal cross-sectional view of still another exampleof the LD module according to the fifth embodiment, having a differentform of a snout from that shown in FIG. 18;

FIGS. 22A to 22C are longitudinal cross-sectional views of still otherexamples of the LD module according to the fifth embodiment, havingdifferent forms of a snout and different forms of a base from the LDmodule shown in FIG. 18;

FIG. 23A is a plan view of a part of a conventional LD module, and FIG.23B is a side view of the part;

FIG. 24 is a longitudinal cross-sectional view of the conventional LDmodule; and

FIG. 25 is a longitudinal cross-sectional view of the conventional LDmodule in the mounting step.

DETAILED DESCRIPTION

Exemplary embodiments of the optical semiconductor module relating tothe present invention will be explained in detail below with referenceto the accompanying drawings. In the following embodiments, constituentparts identical with those of the LD module shown in FIG. 24 aredesignated with like reference symbols.

An optical semiconductor module according to a first embodiment of thepresent invention is an LD module. FIG. 1 is a longitudinalcross-sectional view of the LD module. This LD module 10 differs fromthe conventional LD module shown in FIG. 24, in that a base 11 is fixedonto the bottom plate 8 e instead of the base 6. On the base 11 areprovided, the heat sink 3 mounting thereon the LD element 1 and thethermistor 2, the carrier 5 mounting thereon the PD element 4, and twopieces of support members 11 a supporting the metal ferrule 7 a holdingthe optical fiber 7. The metal ferrule 7 a is fixed to the base 11through the two support members 11 a by YAG laser-welding or soldering.The optical fiber 7 is arranged to pass through the longitudinal hole 8a of the snout 8 b. The portion between the optical fiber 7 and theinternal wall of the snout 8 b is hermetically sealed with a sealant Slike solder. The package 8 is sealed with the lid 9 at the upperopening. The package 8 also has a front wall 8 c and a rear wall 8 dthat faces the front wall 8 c.

FIG. 2 is a top plan view of the package 8. The package 8 is of abutterfly type having a plurality of leads L_(d) protruding from thepackage 8 at both sides. The snout 8 b is covered with a rubber coveringB_(g). A part of the optical fiber 7 that is led out of the package 8 isprotected by a protective tube T_(g). The package 8 has a length L notlarger than 16 millimeter, a width W not larger than 10 millimeter, anda height H not larger than 8 millimeter, as shown in FIGS. 1 and 2.

FIG. 3 is a longitudinal cross-sectional view of a part of the LD moduleshown in FIG. 1, and specifically illustrates the base 11. The base 11differs from the base 6 shown in FIGS. 23A, 23B, 24, and 25, in theshape of the rear end portion to be faced to the rear wall 8 d of thepackage 8. As shown in FIG. 3, the base 11 has a rear end portion Ehaving an upper edge F_(U) and an lower edge F_(L). The lower edge F_(L)is positioned nearer to the front end portion of the base 11 than theupper edge F_(U). In other words, the base 11 has a taper 11 b that isinclined from the vicinity of the upper edge F_(U) toward the lower edgeF_(L), at the rear end portion E. As a result, the formation of thetaper 11 b is equivalent to elimination of the rear lower corner of thebase 11.

FIG. 4 is a longitudinal cross-sectional view of the LD module in themounting step. When the base 11 is mounted into the package 8 in adirection of an arrow mark shown in the FIG. 4, no interference occursbetween the base 11 and the rear wall 8 d of the package 8. This isbecause of the elimination of the rear lower corner of the base 11 bythe taper 11 b. Therefore, the base 11 can be easily mounted onto thebottom plate 8 e of the package 8. Consequently, no significantmisalignment between the LD element 1 and the optical fiber 7 can occurin the mounting step and it is possible to suppress a reduction in thecoupling efficiency between the laser beam emitted from the LD element 1and the optical fiber 7.

Moreover, the prevention of interference between the base 11 and therear wall 8 d results in a prevention of an excessive bend of theoptical fiber 7 at the portion A encircled by the dashed line in FIG. 4.Consequently, the optical fiber 7 can be maintained at a large radius ofbending curvature during the mounting step into the package 8, and isfree from a breakage arising from the excessive bending.

The shape of the rear end portion E of the base 11 is not limited tothat shown in FIG. 3. The rear end portion E may be formed into variousshapes to avoid an interference against the rear wall 8 d in themounting step. For example, the rear end portion may be formed into acurved face 11 c with a curvature radius of r as shown in FIG. 5A, or astep 11 d with a height h2 and a length L1 as shown in FIG. 5B.

In the LD module 10 according to the present embodiment, the base 11 ismounted into the package 8 in the state that the rear end portion E isslightly inclined from a horizontal state such that the optical fiber 7led from the snout 8 b to the outside of the package is not excessivelybent. When the base 11 is formed into the taper 11 b, for example, aheight h1 of the base 11 from its bottom surface to a line ofintersection between the taper 11 b and the rear end surface of the base11 is set to a range of about 0.4≦h1/t≦1.0, where t is a thickness ofthe base 11, as shown in FIG. 3. While an inclination angle of the taperface 11 b is suitably set according to a size of the package 8, aninclination angle θ within a side cross-sectional surface of the base 11parallel to an optical axis is set to a range of about 20°≦θ≦60°. On theother hand, when the base 11 is formed to have the curved face 11 chaving a cylindrical surface or the step 11 d, the radius r of thecylindrical surface (see FIG. 5A) or the height h2 and the length L1 ofthe step (see FIG. 5B) are set to ranges of about 0.4≦r/t, L1/t≦1.0, and0.4≦h2/t≦0.7, where t is a thickness of the base 11.

The optical fiber 7 may be directly fixed with solder Sd, onto a supportmember 11 e that is fixed to the base 11, with no metal ferrule 7 aemployed, as shown in FIGS. 6A and 6B. It is needless to mention thatthe rear end portion E of the base 11 may also be formed into the curvedface 11 c or the step 11 d as shown in FIG. 5A or FIG. 5B. The supportmember 11 e may be made of nonmetal such as ceramic, for example. Whenthe optical fiber 7 is fixed onto the support member 11 e with anadhesive or a synthetic resin, an optical fiber of which externalperiphery is not metal-coated may also be used.

FIG. 7 is a longitudinal cross-sectional view of an LD module accordingto the second embodiment of the present invention. The LD module 15differs from the conventional LD module, in the shape of its package.The LD module 15 is configured as an optical semiconductor module havinga butterfly-type package. As shown in FIG. 7, a snout 108 b of a package108 consists of a first part 108 b ₁ and a second part 108 b ₂. Thesecond part 108 b ₂ has a larger diameter than that of the first part108 b ₁, and is positioned between the first part 108 b ₁ and a frontwall 108 c of the package 108. These first part 108 b ₁ and the secondpart 108 b ₂ have a longitudinal hole 108 a through them, for guidingthe optical fiber 7 to the outside. The longitudinal hole 108 a consistsof a first longitudinal hole 108 a ₁ of the first part 108 b ₁, and asecond longitudinal hole 108 a ₂ of the second part 108 b ₂. Thelongitudinal hole 108 a is, concretely, formed such that an upperboundary F_(UI) of the second longitudinal hole 108 a ₂ is locatedhigher than an upper boundary F_(UO) of the first longitudinal hole 108a1. As a result, the optical fiber 7, when led to the outside of thepackage 108 through the longitudinal hole 108 a, is prevented from beingbrought into contact with the internal surface of the secondlongitudinal hole 108 a ₂. Therefore, an excessive bending deformationof the optical fiber 7 is suppressed.

Consequently, in the LD module 15, in the mounting step of the base 11into the package 108, it is possible not only to maintain a state of alarge bending curvature radius of the optical fiber 7 by the taper 11 bbut also to prevent the optical fiber 7 from being brought into contactwith the internal surface of the second longitudinal hole 108 a ₂ of thesecond part 108 b ₂ of the snout 108 b, as shown in FIG. 8.Consequently, in the LD module 15, it possible to prevent an excessivebending deformation of the optical fiber 7 arising from the interferencebetween the optical fiber 7 and the internal surface of the longitudinalhole 108 a that would otherwise occur at a portion A encircled by adashed line.

The LD module 15 according to the second embodiment has an effect thatthe second part 108 b ₂ provided in the snout 108 b prevents the opticalfiber 7 from being excessively bent, in addition to the effect that thetaper 11 b of the base 11 facilitates the mounting of the base 11 intothe package 108. Therefore, in the LD module 15, it is possible tosuppress a breakage of the metal-coated optical fiber 7 in the mountingstep more surely than in the LD module 10 according to the firstembodiment. Note that the longitudinal hole 108 a may have a pluralityof diameters so as to have three or more steps. The snout 108 b may takea shape other than that shown in FIG. 7, as far as it is possible tosuppress the bending deformation of the optical fiber 7 in the mountingstep. For example, the second part 108 b ₂ of the snout 8 b is inclinedtoward the upper end portion of the front wall 108 c, and the upperboundary F_(UI) of the longitudinal hole 108 a is positioned higher thanthe upper boundary F_(UO).

A package 208 may be used in place of the package 108 (see FIG. 9). Thepackage 208 has a front wall 208 c, a rear wall 208 d, a bottom plate208 e, and a snout 208 b. An external diameter of the snout 208 b isuniform along the longitudinal direction. The snout 208 b has alongitudinal hole 208 a whose diameter is linearly small toward theoutside. In other words, the longitudinal hole 208 a has taper at itsinternal surface along the longitudinal direction. The taper may notnecessarily be formed over the entire of the internal surface along itslongitudinal direction but may be formed at least on a part thereof. Forexample, the taper is formed on only a part of the internal surface nearthe front wall 208 c.

Further, a package 308 may be used in place of the package 108 (see FIG.10). The package 308 has a front wall 308 c, a rear wall 308 d, a bottomplate 308 e, and a snout 308 b having a longitudinal hole 308 a. Thesnout 308 b has a first part 308 b ₁ and a second part 308 b ₂. A partof the longitudinal hole 308 a on the first part 308 b ₁ has a uniformdiameter along the longitudinal direction, and a part of longitudinalhole 308 a on the second part 308 b ₂ has diameter that is linearlysmall toward the first part 308 b ₁. External diameters of the snout 308b are values corresponding to the diameters of the longitudinal hole 308a of the first part 308 b, and of the second part 308 b ₂.

Further, a package 408 may be used in place of the package 108 (see FIG.11). The package 408 has a front wall 408 c, a rear wall 408 d, a bottomplate 408 e, and a snout 408 b having a longitudinal hole 408 a. Theexternal diameter of snout 408 b and the diameter of the longitudinalhole 408 a are linearly small from the front wall 408 c toward theoutside of the package 408.

Furthermore, a package 508 may be used in place of the package 108 (seeFIG. 12). The package 508 has a front wall 508 c, a rear wall 508 d, abottom plate 508 e, and a snout 508 b having a longitudinal hole 508 a.The external and internal faces of snout 508 b are curved such that anexternal diameter of the snout 508 b and a diameter of the longitudinalhole 508 a become gradually small from the front wall 508 c toward theoutside of the package 508.

FIG. 13 is a longitudinal cross-sectional view of a PD module accordingto a third embodiment of the present invention. The PD module differsfrom the LD module shown in FIG. 1, in that the base 11 having thetapered rear end portion E is used for the PD module. The PD module 20is an optical semiconductor module having a butterfly-type package. Acarrier 5 on which a PD element 4 is provided and a metal support member11 e are mounted on the base 11. The metal support member 11 e is fixedonto the base 11 with solder. The support member 11 e may be made ofnonmetal, such as ceramic, for example. The optical fiber 7 coated withmetal is directly fixed onto the metal support member 11 e with solderSd, as shown in FIGS. 13, 14A, and 14B. A portion between the opticalfiber 7 and the internal wall of the snout 8 b is hermetically sealedwith a sealant S like solder or synthetic resin. An upper portion of thepackage 8 is sealed with a lid 9.

The base 11 has the rear end portion E with the tapered face 11 b, likethat shown in FIG. 1. The PD module 20 is formed as explained above.Therefore, as shown in FIG. 15, in the mounting step of the base 11 intothe package 8, it is possible to prevent an interference between thebase 11 and the rear wall 8 d of the package 8. Accordingly, the base 11can be easily mounted into the package 8. Consequently, in the mountingstep, there occurs no misalignment between the PD element 4 and theoptical fiber 7. As a result, it becomes possible to avoid a reductionin the optical coupling efficiency between the PD element 4 and theoptical fiber 7.

Since the rear end portion E of the base 11 has a taper, the opticalfiber 7 is free from excessive bending at a portion A encircled by adashed line in FIG. 15 when mounting the base 11 into the package 8 withthe optical fiber 7 being inserted through the longitudinal hole 8 a.Since the optical fiber 7 maintains a state of a large bending curvatureradius, a breakage of the optical fiber 7 is avoided.

The rear end portion E of the base 11 may be formed into various shapes,such as, for example, the curved face 11 c or the step 11 d as shown inFIG. 5A or FIG. 5B.

FIG. 16 is a longitudinal cross-sectional view of a package of a LDmodule according to a fourth embodiment. The LD module 30 differs fromthe LD module 10 according to the first embodiment in the type ofpackage. Concretely, in the LD module 30, a package 608 closed with alid 609 is a DIL-type. FIG. 17 is a top plan view of the package of theLD module 30.

As shown in FIGS. 16 and 17, the LD module 30 has a plurality of leadsLd extending downward from the side surfaces of the package 608. Anunillustrated snout of the package 608 is covered with a rubber coveringB_(g), and a part of the optical fiber 7 that is led out of the package608 is protected by a protective tube T_(g). The package 608 has alength L not larger than 16 millimeter, a width W not larger than 10millimeter, and a height H not larger than 8 millimeter. The base 11shown in one of FIG. 3 and FIGS. 5A to 6B is mounted into the package 8.

Therefore, although the LD module 30 is very small, the base 11 can beeasily mounted into the package 608. Consequently, it is possible toavoid a reduction in the coupling efficiency between the laser beamemitted from the LD element 1 to the optical fiber 7.

Since a rear end portion E of the base 11 is formed into the taper 11 b,a curved face 11 c, or a step 11 d, the optical fiber 7 is notexcessively bent in the mounting step. As a result, the optical fiber 7can be maintained at a large bending curvature radius, and thus freefrom breakage in the mounting step.

Note that if a longitudinal hole through which the optical fiber 7passes is formed to have a larger size at the inside than at the outsideof the package 608 as shown in FIGS. 7 to 12, it is possible to moresurely suppress an excessive bending deformation of the optical fiber 7in the mounting step, thereby to surely avoid a breakage of the opticalfiber 7.

FIG. 18 is a longitudinal cross-sectional view of a LD module accordingto a fifth embodiment of the present invention. The LD module 35 differsfrom the optical semiconductor modules according to the first throughthe fourth embodiments, in a base and a lid of a package. In the firstthrough the fourth embodiment, the rear end portion of the base 11 or alongitudinal hole 708 a provided in the snout 708 b of a package 708 wasprocessed in various ways. On the other hand, in the LD module 35, abutterfly-type or DIL-type package 708 fails to have a rear wall at aside opposite to the snout 708 b, or it has a rear wall with at least apart thereof removed.

For example, in the LD module 35 shown in FIG. 18, the butterfly-type orDIL-type package 708 has no rear wall opposite to a front wall 708 c.Instead, the wall that faces the front wall 708 c is replaced by aperpendicular plate 709 a that is integrated with a lid 709.

Therefore, as shown in FIG. 19, the package 708 is open at the rear sidethereof (i.e., at the left side in FIG. 18 and FIG. 19) when mountingthe base 11 onto the bottom plate 708 e. Hence, it is possible to insertthe base 11 into the package 708 from the left without causinginterference of the optical fiber 7 with the inner wall of thelongitudinal hole 708 a at its end exposed on the front wall 708 c. Itis substantially unnecessary to curve the optical fiber 7 at a portion Aof the package 708 encircled by a dashed line. Since the optical fiber 7can be maintained at a large bending curvature radius, a breakage of theoptical fiber 7 is avoided. Further, it becomes possible to avoid areduction in the optical coupling efficiency between the LD element 1and the optical fiber 7.

Another package and lid in place of the package 708 and the lid 709 maybe used if the package is open at the side opposite to the snout beforeclosing with the lid. For example, as shown in FIG. 20, a package 808 inplace of the package 708 may be used for an LD module 45, wherein theupper portion of a rear wall 808 d opposite to a front wall 808 c isremoved, and a perpendicular plate 809 b provided integrally with thelid 809 may be located at this removed portion.

Since the optical fiber 7 can be inserted horizontally in thisembodiment, a snout may be formed to have a longitudinal hole 908 a witha diameter that is uniform in the longitudinal direction, as shown inFIG. 21.

These LD modules shown in FIGS. 20 and 21 make the mounting step easy,without substantially bending the optical fiber 7, in a similar mannerto that shown in FIG. 19. Further, the rear end portion E of the base 11may have a taper, a curved face or a step, like that shown in FIG. 3,FIG. 5A, or FIG. 5B, whereby it is possible to prevent the optical fiber7 from being excessively bent due to the interference between the rearend portion E of the base 11 and the residual rear wall 808 d, in themounting step.

In addition, a snout of the package may have forms other than thoseshown in FIGS. 18 and 21. For example, LD modules 65, 75, and 85 shownin FIGS. 22A to 22C have packages 1008, 1108, and 1208, respectively. Asnout 1008 b of the package 1008 shown in FIG. 22A corresponds to thesnout 208 b shown in FIG. 9, a snout 1108 b of the package 1108 shown inFIG. 22B corresponds to the snout 308 b shown in FIG. 10, and a snout1208 b of the package 1208 shown in FIG. 22C corresponds to the snout408 b shown in FIG. 11.

These package may be used for not only the LD module but also the PDmodule according to the third embodiment.

Advantages derived from the present invention may include one or more ofthe following.

According to one or more embodiment of the present invention, it is easyto mount the base into the package.

According to one or more embodiment of the present invention, it ispossible to avoid a reduction in the coupling efficiency between theoptical fiber and the optical semiconductor element.

According to one or more embodiment of the present invention, it ispossible to prevent the optical fiber from being excessively bent,thereby to maintain the state of a large radius of bending curvature andprevent a breakage of the optical fiber.

Although the invention has been described with respect to a specificembodiment for a complete and clear disclosure, the appended claims arenot to be thus limited but are to be construed as embodying allmodifications and alternative constructions that may occur to oneskilled in the art which fairly fall within the basic teaching hereinset forth.

1. An optical semiconductor module including a base having installedthereon an optical fiber and an optical semiconductor element, and apackage which houses the base on a bottom thereof and has a first sidewall with an optical section through which the optical fiber is led anda second side wall facing the first side wall, wherein: the base is cutoff to form a curved surface with respect to the bottom at a lowercorner on a side of the base facing the second side wall of the housing,and a ratio of r/t is from 0.4 to 1.0, where t is a thickness of thebase, and r is a curvature radius of the curved surface.
 2. An opticalsemiconductor module including a base having installed thereon anoptical fiber and an optical semiconductor element, and a package whichhouses the base on a button thereof and has a first side wall with anoutlet section through which the optical fiber is led and a second sidewall facing the first wall, wherein the base is cut off to form aterrace at a lower corner on a side of the base facing the second sidewall of the housing, wherein a ratio of h/t is form 0.4 to 1.0 and ratioof L/t if from 0.4 to 1.0, where t is a thickness of the base, h is adistance between the terrace and the bottom, and L is a width of theterrace.
 3. The optical semiconductor module according to claim 1,wherein the outlet section is a snout-like outlet with a through hole, across-section of which at the base thereof is larger than that of thethrough hole at a free edge thereof.
 4. The optical semiconductor moduleaccording to claim 2, wherein the outlet section is a snout-like outletwith a through hole, a cross-section of which at the base thereof islarger than that of the thought hole at a free edge thereof.
 5. Theoptical semiconductor module according to claim 3, wherein a diameter ofthe thought hole is at the base is larger than a diameter of the throughhole at the free edge.
 6. The optical semiconductor module according toclaim 4, wherein a diameter of the through hole at the base is largerthan a diameter of the through hole at the free edge.
 7. The opticalsemiconductor module according to claim 3, wherein the optical fiberincludes an optical fiber connected to a lens.
 8. The opticalsemiconductor module according to claim 4, wherein the optical fiberincludes an optical fiber connected to a lens.
 9. The opticalsemiconductor module according to claim 1, wherein the opticalsemiconductor element includes at least one of a semiconductor laserelement or a photodiode element.
 10. The optical semiconductor moduleaccording to claim 2, wherein the optical semiconductor element includesat least one of a semiconductor laser element of a photodiode element.11. The optical semiconductor module according to claim 1, wherein theoptical fiber is coated with a metal.
 12. The optical semiconductormodule according to claim 2, wherein the optical fiber is coated with ametal.